1. Field of the Invention
The present invention relates to sulfur-containing heterocyclic compounds and salts thereof which are useful for treatment of osteoporosis.
The compounds and salts according to the present invention possess bone resorption inhibitory activity, and they inhibit the quantitative loss of bone due to release of calcium from bones into blood.
2. Description of the Prior Art
Osteoporosis is known as a disease associated with the loss of bone calcium into the blood with the consequent decrease of bone mass which causes the bones to become fragile and liable to be fractured.
The cardinal manifestations of osteoporosis are kyphosis and fracture of thoracic vertebrae, lumber vertebrae, femoral neck, distal ends of radii, ribs, proximal ends of humeri and so on. The cause of such malady varies from endocrine disorder to nutritional disorder. The therapeutic drugs used in such cases are estrogens, calcitonin (calcium regulating hormone), vitamin D, calcium preparations and so on.
However, these therapeutic approaches are not effective enough in that symptoms and patients which can be treated are limited and, moreover, they are not definitely effective in preventing or alleviating the loss of bone mass.